Process for the hydrogenative cracking of a hydrocarbon oil to produce lubricating oil



US. Cl. 20859 7 Claims ABSTRACT OF THE DISCLOSURE High quality lubricating oil is prepared from high boiling oils by hydrocracking in a first stage to a conversion of -65% weight to products boiling below 525 C., removing the low boiling products and converting the high boiling residue in a second hydrocracking zone to provide a 20-75% high boiling residue in the second stage liquid product, and recovering from the second stage product lubricating oil boiling in the range from 370- 525 C.

This invention relates to a process for the hydrogenative cracking of a hydrocarbon oil to produce lubricating oil.

A process is known for the hydrogenative cracking of a hydrocarbon oil in two stages for the preparation of gasoline having a relatively high octane number. By means of this method a hydrocarbon oil is contacted in the presence of hydrogen in a first stage with a catalyst under such circumstances that only a slight degree of cracking takes place, whereupon the entire reaction product is contacted in the presence of hydrogen in a second stage with a catalyst under such circumstances that gasoline having a comparatively high octane number is formed. This process has the drawback that it is not suitable for the preparation of high-grade lubricating oil.

It has now been found that high-grade lubricating oil can be prepared by hydrogenatively cracking a hydrocarbon oil in a first reaction zone, by subsequently separating off a hydrogen-containing gas and one or more lower-boiling hydrocarbon fractions from the reaction product, and by then hydrogenatively cracking the remaining higher-boiling part of the reaction product in a second reaction zone.

The invention relates, therefore, to a process for the preparation of lubricating oil by hydrogenative cracking of a hydrocarbon oil, which comprises contacting the hydrocarbon oil in the presence of hydrogen or a hydrogen-containing gas in a first reaction zone with a catalyst comprising a hydrogenation component and an acid-acting cracking component, under such conditions that the net yield of hydrocarbons boiling at 525 C. and below in the first reaction zone is about 5% to 65% by weight higher than that in the feed, separating from the first reaction zone efiluent a hydrogen-containing gas and one or more hydrocarbon fractions having a final boiling point (F.B.P.) of not more than 525 C., contacting at least a portion of the higher boiling portion of the reaction product in the presence of hydrogen or a hydrogen-containing nited States Patent 0 3,444,071 Patented May 13, 1969 gas in a second reaction zone with a catalyst comprising a hydrogenation component and an acid-acting cracking component, and recovering from the second reaction zone effiuent a lubricating oil fraction boiling in the temperature range from about 370 to 525 C. Both the first and second reaction zones consist of one or more reactors.

In the preparation of high-grade lubricating oil, the starting material should be a hydrocarbon oil having a boiling range wholly or partly above the F.B.P. of the desired lubricating oil. Hydrocarbon oils suitable for use as starting materials for the first reaction zone are a distillate or residue obtained by atmospheric distillation of crude petroleum or a distillate or residue obtained in the vacuum distillation of a residual oil fraction. It is also possible to subject a residue or distillate to visbreaking a treatment for lowering the viscosity or to a catalytic cracking treatment, and to use one or more of the resultant distillates as starting material for the process according to the present invention. It is, of course, possible in the present process to prepare other products such as kerosene, gas oil and the like simultaneously with lubricating oil.

In the preparation of high-grade lubricating oil, it is preferable to carry out the hydrogenative cracking in the first reaction zone under such conditions that the content of hydrocarbons boiling between 370 C. and 525 C. in the hydrocarbon mixture leaving the first reaction Zone is not less than 5% by weight and not more than 50% by weight higher than that of the hydrocarbon oil passed into the first reaction zone. Very suitable conditions are those whereby the content of hydrocarbons boiling between 370 C. and 525 C. in the hydrocarbon mixture leaving the first reaction zone is from 10 to 30% by weight higher than that of the hydrocarbon oil passed into the first reaction zone.

The desired degree of hydrogenative cracking can be adjusted by the combination of catalyst, temperature, space velocity, pressure, and hydrogen/ oil ratio. Since the eifect of the pressure, and in particular of the ratio of hydrogen to oil is of less importance on the hydrogenative cracking it can be stated that the desired conversion into lower-boiling fractions can be effected in particular by the variation of the temperature, by the space velocity and by the choice of catalyst.

The conditions under which the hydrogenative cracking in the first reaction zone takes place are preferably as follows: temperature between 250 C. and 475 C.; space velocity between 0.4 and 5 volumes of oil per hour per volume of catalyst; pressure between 50 atm. and 500 atm.; ratio of hydrogen to oil between about 1,500 and 30,000 standard cubic feet of hydrogen per barrel of oil (s.c.f./b.).

If a very active catalyst is used in the first reaction zone the conditions in this zone must be selected on the rather mild side, in order to obtain no more than the desired degree of hydrogenative cracking. For example, a temperature of 300 C. and a space velocity of 4 may be used in such a case. On the other hand, if the catalyst in the first reaction zone is not very active, more severe conditions must be selected in this zone in order to obtain the desired degree of hydrogenative cracking. It is preferred in such a case to choose a temperature of 400 C. and a liquid hourly space velocity of 2.

The hydrocracking catalyst used in either zone comprises a hydrogenation component and an acid-acting cracking component. The hydrogenation component is preferably one or more metals of the Groups 18, VIB or VIII of the Periodic Table of Elements and/ or their sulfides and/or their oxides. Preferably the hydrogenation component is one or more of the metals cobalt, nickel, tungsten, molybdenum, platinum, palladium, copper and/ or silver and/or the sulfides and/or oxides thereof. The amount of hydrogenative metal is generally about 1% to 25% weight.

The acid-acting cracking component of the catalyst preferably comprises silica, alumina, magnesia, zirconia, titania and/or boria. In addition, the cracking component has from about 0.1% by weight to 8% by weight of fluorine, based on the total weight of the catalyst. The silica content of the carrier in the second reaction zone is preferably not more than 50% by weight; very good results are achieved with a silica content of between 15% by weight and 20 by weight.

Liquid efiiuent from the first reaction zone is fractionated to remove hydrocarbons boiling at 525 C. or below. The low boiling hydrocarbons can in turn be again separated into one or more fractions, including one or more lubricating oil fractions boiling bet-ween 370 C. and 525 C. The lubricating oil fractions obtained from the first reaction zone efiluent are of a less satisfactory quality than the lubricating oil fractions recovered in the second reaction zone. The lower boiling material which has been separated from the first stage cracking product appears to be an excellent feedstock for the production of gasoline by hydrocracking. The gasoline thus obtained has a high octane number.

At least a portion of the high boiling part of the first reaction zone product is contacted, wholly or partly, in a second reaction zone in the presence of hydrogen and/ or of a hydrogen-containing gas with a catalyst comprising a hydrogenation component and an acid-acting cracking component. If desired, a portion of the high boiling product can be recycled to the first reaction zone.

The desired high-grade lubricating oil product is obtained from the second reaction zone product. Hydrogenative cracking in the second recation zone is carried out under such conditions that the liquid product from this reaction zone contains from 20% to 75% by weight of hydrocarbons boiling above 525 C. Very suitable conditions are those whereby the liquid product leaving the second reaction zone contains between 40% and 60% by weight of a residue having an -I.B.P. of 525 C.

The hydrogenative cracking in the second reaction zone is preferably carried out at a temperature between 325 C. and 440 C., a space velocity between 0.2 and volumes of oil per hour per volume of catalyst, a pressure between .50 atm. and 500 atm. and a hydrogen/oil ration of between 1,500 and 30,000 s.c.f./b.

If a very active catalyst is used in the second reaction zone, the conditions in this zone must be selected on the rather milder side in order to obtain no more than the desired degree of cracking. For example, with such a catalyst, a temperature of 400 C. and a liquid hourly space velocity of 1.7 may be taken. On the other hand, if the catalyst in the second reaction zone is-not so active, more severe conditions must be selected in this zone inorder to obtain the desired degree of hydrogenative cracking. With such less active catalyst, it is preferred for-example, to choose a temperature of 450 C.- and a liquid hourly space velocity of 0.8.

. As has been stated above, the nature of the'hydrocarbon oilpassed into the firstreaction zone must also be carefully considered inthe choice ofvthe reaction conditions. Also, it should be noted in this connection that if the feed to the first reaction zone contains nitrogen compounds, these will be decomposed to a considerable extent during the hydrogenative cracking, with the formation of ammonia. This ammonia is preferably removed by injecting water into the first reaction zone product. The ammonia dissolves in the water, which is subsequently separated from the hydrocarbon product. After one or more lower-boiling fractions have been separated from the reaction product leaving the first reaction zone, as mentioned hereinbefore, the remaining part is passed to the second reaction zone. This remaining part will generally possess a much smaller concentration of nitrogen compounds than the original feed to the first reaction zone. Itis well known that nitrogen compounds lower the activity of hydrogenation cracking catalysts. For these reasons the reaction conditions in the second reaction zone can be milder than in the first stage. \In the second reaction zone, for example, a lower temperature can be used than was required in the first reaction zone.

A hydrogen-containing gas and one or more low boiling hydrocarbon fractions having a F. B.P. of not more than 525 C. is separated from the second reaction zone product. Preferably all or a portion of the higher boiling product is recycled to the second reaction zone. From the low boiling hydrocarbon fractions, a lubricating oil fraction boiling in the range from about 370 C. to 525 C. is obtained, and, if desired other low boiling hydrocarbon product fractions. The lubricating oil fraction obtained in this manner is very suitable for the preparation of finished lubricating oil products. If desired, the lubircating oil product fraction recovered from the second reaction zone can be subjected to additional processing, such as dewaxing, to improve other desired characteristics of the oil. ilt is to be noted that lubricating oils of high viscosity index (Dean-Davis), i.e., above 80, and preferably above 90, can be prepared by the process of the invention.

Feed to the process may sometimes contain carbonaceous components which have a tendency to deposit on the catalyst, and other impurities such as the nitrogen compounds mentioned above which suppress cracking and/or may deposit on the catalyst. It is generally preferred to subject the feed to a suitable pretreatment in order to remove the carbonaceous components and/ or to lower the nitrogen content. Suitable ways of doing this include a treatment with concentrated sulfuric acid, or a catalytic hydrogenation treatment with, for example, a catalyst comprising cobalt, nickeland/or molybdenum on a suitable support such as alumina.

As a rule, a pretreatment also reduces thesul'fur content of the hydrocarbon oil. Since, however, sulfur compounds have a favorable effect on the activity of some hydrogenation cracking catalysts, it may be advantageous to inject hydrogen sulfide and/or other sulfur compounds in the feed to the first and/or second re action zone'. Such injectioncf sulfur compounds can also be carried out in the case Where the hydrocarbon feed to the first reaction zone has a naturally low sulfur content, I

The hydrogen-containing gas which'is separated from the reaction product from the first reaction zone can, if desired after reduction of the ammonia content, be recycled to this reaction zone. This gas can also be passed into the second reaction zone. Similarly, the hydrogen-containing gas which is separated'from the second reaction zone product can be recycled to the second reaction zone, prefe'rablyafter reduction of the ammonia content. It is also possible to mix the ,two hydrogenf containing gases which have ,beenseparated to reduce the ammonia contentofthe mixture, and to pass onepart of the purified mixture, into the first reaction zone and another partinto the second reactionzone. The reduction of the ammoniacontent of the hydrogen-containing gas can be effected in a manner'known per, se. l

If an extremely'high sulfur content oil is used as feed to the first reaction' 'zone, itmay be desirable to remove hydrogen sulfidefrom the recycle gas. Thispurification can likewise be effected in a known manner.

EXAMPLE A residual oil having a specific gravity of 0.994, a sulfur content of 3.8% by weight, a nitrogen content of 3000 p.p.m.W. and a kinematic viscosity at 100 C. of 225 cs. was converted into a high-grade gas oil and a high-grade lubricating oil by means of the process according to the invention. The feed, which contained approximaately 2% by weight of hydrocarbons boiling below 510 C., was passed together with hydrogen into a first reactor at a temperature of 420 C., a liquid hourly space velocity of 0.5, a pressure of 150 atm. and a hydrogen/oil ratio of about 17,000 s.c.f./b. The catalyst contained 3% by weight cobalt, by weight molybdenum, 5% by weight fluorine and 82% by weight alumina.

A hydrogen-containing gas was separated from the product from the first reactor and returned to the reactor. A gas fraction containing pentane, lighter hydrocarbons, NH and H S, a gasoline fraction, a gas oil fraction and a lubricating oil fraction were fractionated from the liquid product. A finished lubricating oil was obtained from the lubricating oil fraction by means of dewaxing. The properties of the gas oil and the lubricating oil are shown in Table I.

TAB LE I Gas oil obtained erties of the gas oil and the lubricating oil are given in Table I. This table shows that the gas oil and the lubricating oil obtained from the second stage by means of the process according to the invention possess properties superior to those of the gas oil and the lubricating oil obtained from the first stage, or of the gas oil and lubricating oil obtained from the second stage without separation of lower-boiling fractions from the first reactor product.

Table II shows a material balance for the process according to the invention and for the process in which no lower-boiling fractions were separated from the product from the first reactor. The hydrogen consumption in both cases was approximately 4% by weight, based on the starting material.

Lubricating oil without separa- Lubricating obtained without Gas oil from stage tion of fractions oil from stage separation of from product fraction from I II from stage I I II from stage I I.B.P., O 181 175 180 375 381 368 F.B.P., 367 361 364 510 520 507 Specific gravity 0. 865 0. 850 0.860 0. 910 0. 866 0. 903 Sulfur content, percent w 0. 15 0. 05 0. 06 0. 15 0. 10 0. 10 Nitrogen content, p.p.n1. w 110 14 17 550 70 105 Kinematic viscosity at 100 0., cs 9 8 9 Viscosity index 67 94 71 Diesel index 38 46 41 After the hydrocarbon fractions boiling below 510 C. had been separated, the remaining part of the reaction product from the first reactor was passed, together with a supply of hydrogen, to a second stage reactor at a temperature of 420 C., a liquid hourly space velocity of 0.5, a pressure of 170 atm. and at a hydrogen/ oil ratio of about 17,000 s.c.f./b. The catalyst in the second reactor contained 3% by weight nickel, 8% by weight tungsten, 3% by weight fluorine, 21.5% by weight silica and 64.5% by weight alumina.

A hydrogen-containing gas was separated from the second reactor reaction product and passed back to the second reactor. Liquid product was fractionated into a fraction containing pentane, lighter hydrocarbons, H 8 and NH a gasoline fraction, a gas oil fraction, a lubricating oil fraction, and a residue which amounted to approximately 59% by weight of the product from the second reactor. Approximately half of the residue was recycled to the second stage. The lubricating oil fraction was dewaxed to obtain a finished lubricating oil. The properties of the gas oil and the lubricating oil are listed in Table I.

Subsequently, a feed identical to that used in the experiment described above was hydrogenatively cracked in the first and second reactors under the same conditions as stated above. On this occasion, however, no gas, gasoline, gas oil or lubricating oil fractions were separated from the liquid product of the first reactor; instead, this reaction product was passed in its entirety direct to the second reactor. The reaction product from the second reactor was separated, after separation of a hydrogencontaining gas, into a gas fraction containing pentane, lighter hydrocrbons, H 5 and NH a gasoline fraction, a gas oil fraction and a lubricating oil fraction, in addition to a residue which amounted to approximaately 59% by weight of the product from the second reactor. Approximately half the residue was recycled to the second stage. A finished lubricating oil was obtained from the lubricating oil fraction by means of dewaxing. The prop- I claim as my invention:

1. A process for preparing lubricating oil which comprises contacting in a first reaction zone a feed comprising hydrocarbons boiling above lubricating oil boiling range with a catalyst comprising a hydrogenation component and an acid-acting refractory oxide cracking component under hydrogenative cracking conditions to eifect a net yield of hydrocarbon boiling at 525 C. and below of about 5% to 65% by Weight, separating from the first reaction zone liquid efiluent hydrocarbons boiling at about 525 C. and below, contacting at least a portion of higher boiling liquid efiluent in a second reaction zone with a catalyst comprising a hydrogenation component and an acid-acting refractory oxide cracking component under hydrogenative cracking conditions to provide a liquid product having from about 20% to 75% by weight hydrocarbons boiling above about 525 C., and recovering from the second reaction zone liquid efliuent at least one lubricating oil fraction boiling in the range from about 370 to 525 C.

2. The process according to claim 1 wherein the hydrogenative cracking conditions in the first reaction zone are a temperature of about 250 to 475 C., a liquid hourly space velocity of about 0.4 to 5, and a pressure of about 50 to 500 atmospheres, and hydrogenative cracking conditions in the second reaction zone are a temperature of about 325 to 440 C., a liquid hourly space velocity of about 0.2 to 5, and a pressure of about 50 to 500 atmospheres.

3. The process according to claim 2 wherein the catalyst in the second reaction comprises from about 0.1% to 8% by weight fluorine an acid-acting refractory oxide cracking component having no more than 50% by weight silica.

4. The process according to claim 2 wherein the net yield of hydrocarbons boiling between 370 and 525 C. from the first reaction zone is about 5% to 50% by weight.

5. The process according to claim 1 wherein the lubricating oil recovered from the second reaction zone liquid product has a viscosity index above 80.

6. The process according to claim 1 wherein a high quality gas oil fraction is recovered from the second reaction zone liquid product.

7. The process according to claim 1 wherein at least a portion of second reaction zone liquid product boiling above about 525 C. is recycled to the second reaction zone.

8 References Cited UNITED STATES PATENTS 3/1966 Paterson 2081 11 3/1967 Kozlowski 2081 11 DELBERT E. GANTZ, Primary Examiner.

T. H. YOUNG, Assistant Examiner. 

